DESCRIPTION: The focus of this project will be to elucidate the mechanism of spectral tuning in the subgroup of short-wave visual pigments. First, the protonation state of the Schiff base nitrogen in the 11-cis retinal chromophore of the ultraviolet, human blue and bovine blue pigments will be determined by 15N-solid state magic angle spinning (MAS) NMR spectroscopy. Second the amino acid residues responsible for spectral tuning within the short-wave group will be identified. Finally the mechanism of spectral tuning in the short-wave subgroup will be compared to that of other subgroups of visual pigments. In particular, attention will be focused on the zebrafish blue pigment because it is a member of the middle-wavelength subgroup of pigments (based on its amino acid sequence) but has a maximum centered in the short wavelength range (419nm). Results from this work will shed light on the mechanisms of spectral tuning among the visual pigments to illuminate the mechanistic basis for the evolutionary development of human color vision.